The overall goal of this program is to characterize the molecular basis for tumor cell adaptation to limitations in oxygen and nutrients. Oxygen and/or nutrient deprivation develops as cells within solid tumors accumulate in excess of physiological numbers supportable by the existing vascular system. Therefore, developing tumors are typically subjected to oxygen limitation and nutrient deprivation. The accumulation of non-transformed cells is inhibited under these conditions because hypoxia/nutrient deprivation leads to the initiation of apoptosis. In contrast, most tumor cells are defective in their apoptotic response, and therefore, fail to engage programmed cell death. Our central hypothesis is that tumor cells both suppress apoptosis and alter their metabolism to survive until new blood vessels grow, The goal of Project I is to identify metabolic pathways that allow tumor cells to adapt and grow under these conditions. This project will determine how cells simultaneously activate beta-oxidation to support ATP production while maintaining the level of fatty acid synthesis required for cell growth during glucose deprivation. Project I will also examine how hypoxic tumor cells coordinate protein and lipid synthesis when hypoxia inducible factor (H IF) activation results in diversion of available glucose away from macromolecular synthesis into anaerobic glycolysis. The experiments outlined in Project 2 will focus on metabolic outcomes of c-Myc, mTOR, and p53 modulation by oxygen limitation and HIF activation. HlFs influence anabolic metabolism, proliferation, protein synthesis, and DNA repair in transformed cells via these central regulatory pathways. Experiments proposed in Project 3 are based on the hypothesis that PERK (as a sensor of cellular nutrient availability) functions as a critical pro-survival factor via activation of a transcriptional program that promotes cellular adaptation to nutrient restriction thereby facilitating tumor growth. In this project, the contribution of PERK to the regulation of redox homeostasis and lipid biosynthesis will be evaluated. Through collaborations facilitated by this program project, we will investigate mechanisms whereby glucose limitation (Project 1) and oxygen deprivation (Project 2) regulate cellular responses to the microenvironment. Finally, how this contributes to redox homeostasis and genome integrity will be evaluated in Project 3. All three projects will make frequent use of the Metabolic Core which will provide assays for the analysis of cellular bioenergetics and an Administrative Core which will provide administrative oversight, budgetary management, and the organization of meetings with the external advisory board. Extensive points of collaboration have already been established between all three projects in the previous funding cycle. We anticipate that our collective efforts will provide novel insights into metabolic changes that characterize malignant cell adaptation under conditions of decreased oxygen and nutrient availability.